rhg: Skip reading the contents of ambiguous files in some cases

If the size of the file in the working directory does not match the length of
the filelog data, we know its contents will be different and don’t need to
read it.

rhg still decodes the filelog revision, which is not needed in some cases.

Differential Revision: https://phab.mercurial-scm.org/D11910

rust/rhg/src/commands/status.rs

@@ -1,494 +1,506
 // status.rs
 //
 // Copyright 2020, Georges Racinet <[e-mail]>
 //
 // This software may be used and distributed according to the terms of the
 // GNU General Public License version 2 or any later version.
 
 use crate::error::CommandError;
 use crate::ui::Ui;
 use crate::utils::path_utils::RelativizePaths;
 use clap::{Arg, SubCommand};
 use format_bytes::format_bytes;
 use hg;
 use hg::config::Config;
 use hg::dirstate::has_exec_bit;
 use hg::dirstate::status::StatusPath;
 use hg::dirstate::TruncatedTimestamp;
 use hg::dirstate::RANGE_MASK_31BIT;
 use hg::errors::{HgError, IoResultExt};
 use hg::lock::LockError;
 use hg::manifest::Manifest;
 use hg::matchers::AlwaysMatcher;
 use hg::repo::Repo;
 use hg::utils::files::get_bytes_from_os_string;
 use hg::utils::files::get_path_from_bytes;
 use hg::utils::hg_path::{hg_path_to_path_buf, HgPath};
 use hg::StatusOptions;
 use log::{info, warn};
 use std::io;
 use std::path::PathBuf;
 
 pub const HELP_TEXT: &str = "
 Show changed files in the working directory
 
 This is a pure Rust version of `hg status`.
 
 Some options might be missing, check the list below.
 ";
 
 pub fn args() -> clap::App<'static, 'static> {
     SubCommand::with_name("status")
         .alias("st")
         .about(HELP_TEXT)
         .arg(
             Arg::with_name("all")
                 .help("show status of all files")
                 .short("-A")
                 .long("--all"),
         )
         .arg(
             Arg::with_name("modified")
                 .help("show only modified files")
                 .short("-m")
                 .long("--modified"),
         )
         .arg(
             Arg::with_name("added")
                 .help("show only added files")
                 .short("-a")
                 .long("--added"),
         )
         .arg(
             Arg::with_name("removed")
                 .help("show only removed files")
                 .short("-r")
                 .long("--removed"),
         )
         .arg(
             Arg::with_name("clean")
                 .help("show only clean files")
                 .short("-c")
                 .long("--clean"),
         )
         .arg(
             Arg::with_name("deleted")
                 .help("show only deleted files")
                 .short("-d")
                 .long("--deleted"),
         )
         .arg(
             Arg::with_name("unknown")
                 .help("show only unknown (not tracked) files")
                 .short("-u")
                 .long("--unknown"),
         )
         .arg(
             Arg::with_name("ignored")
                 .help("show only ignored files")
                 .short("-i")
                 .long("--ignored"),
         )
         .arg(
             Arg::with_name("copies")
                 .help("show source of copied files (DEFAULT: ui.statuscopies)")
                 .short("-C")
                 .long("--copies"),
         )
         .arg(
             Arg::with_name("no-status")
                 .help("hide status prefix")
                 .short("-n")
                 .long("--no-status"),
         )
 }
 
 /// Pure data type allowing the caller to specify file states to display
 #[derive(Copy, Clone, Debug)]
 pub struct DisplayStates {
     pub modified: bool,
     pub added: bool,
     pub removed: bool,
     pub clean: bool,
     pub deleted: bool,
     pub unknown: bool,
     pub ignored: bool,
 }
 
 pub const DEFAULT_DISPLAY_STATES: DisplayStates = DisplayStates {
     modified: true,
     added: true,
     removed: true,
     clean: false,
     deleted: true,
     unknown: true,
     ignored: false,
 };
 
 pub const ALL_DISPLAY_STATES: DisplayStates = DisplayStates {
     modified: true,
     added: true,
     removed: true,
     clean: true,
     deleted: true,
     unknown: true,
     ignored: true,
 };
 
 impl DisplayStates {
     pub fn is_empty(&self) -> bool {
         !(self.modified
             || self.added
             || self.removed
             || self.clean
             || self.deleted
             || self.unknown
             || self.ignored)
     }
 }
 
 pub fn run(invocation: &crate::CliInvocation) -> Result<(), CommandError> {
     let status_enabled_default = false;
     let status_enabled = invocation.config.get_option(b"rhg", b"status")?;
     if !status_enabled.unwrap_or(status_enabled_default) {
         return Err(CommandError::unsupported(
             "status is experimental in rhg (enable it with 'rhg.status = true' \
             or enable fallback with 'rhg.on-unsupported = fallback')"
         ));
     }
 
     // TODO: lift these limitations
     if invocation.config.get_bool(b"ui", b"tweakdefaults")? {
         return Err(CommandError::unsupported(
             "ui.tweakdefaults is not yet supported with rhg status",
         ));
     }
     if invocation.config.get_bool(b"ui", b"statuscopies")? {
         return Err(CommandError::unsupported(
             "ui.statuscopies is not yet supported with rhg status",
         ));
     }
     if invocation
         .config
         .get(b"commands", b"status.terse")
         .is_some()
     {
         return Err(CommandError::unsupported(
             "status.terse is not yet supported with rhg status",
         ));
     }
 
     let ui = invocation.ui;
     let config = invocation.config;
     let args = invocation.subcommand_args;
     let all = args.is_present("all");
     let display_states = if all {
         // TODO when implementing `--quiet`: it excludes clean files
         // from `--all`
         ALL_DISPLAY_STATES
     } else {
         let requested = DisplayStates {
             modified: args.is_present("modified"),
             added: args.is_present("added"),
             removed: args.is_present("removed"),
             clean: args.is_present("clean"),
             deleted: args.is_present("deleted"),
             unknown: args.is_present("unknown"),
             ignored: args.is_present("ignored"),
         };
         if requested.is_empty() {
             DEFAULT_DISPLAY_STATES
         } else {
             requested
         }
     };
     let no_status = args.is_present("no-status");
     let list_copies = all
         || args.is_present("copies")
         || config.get_bool(b"ui", b"statuscopies")?;
 
     let repo = invocation.repo?;
 
     if repo.has_sparse() || repo.has_narrow() {
         return Err(CommandError::unsupported(
             "rhg status is not supported for sparse checkouts or narrow clones yet"
         ));
     }
 
     let mut dmap = repo.dirstate_map_mut()?;
 
     let options = StatusOptions {
         // we're currently supporting file systems with exec flags only
         // anyway
         check_exec: true,
         list_clean: display_states.clean,
         list_unknown: display_states.unknown,
         list_ignored: display_states.ignored,
         list_copies,
         collect_traversed_dirs: false,
     };
     let (mut ds_status, pattern_warnings) = dmap.status(
         &AlwaysMatcher,
         repo.working_directory_path().to_owned(),
         ignore_files(repo, config),
         options,
     )?;
     if !pattern_warnings.is_empty() {
         warn!("Pattern warnings: {:?}", &pattern_warnings);
     }
 
     for (path, error) in ds_status.bad {
         let error = match error {
             hg::BadMatch::OsError(code) => {
                 std::io::Error::from_raw_os_error(code).to_string()
             }
             hg::BadMatch::BadType(ty) => {
                 format!("unsupported file type (type is {})", ty)
             }
         };
         ui.write_stderr(&format_bytes!(
             b"{}: {}\n",
             path.as_bytes(),
             error.as_bytes()
         ))?
     }
     if !ds_status.unsure.is_empty() {
         info!(
             "Files to be rechecked by retrieval from filelog: {:?}",
             ds_status.unsure.iter().map(|s| &s.path).collect::<Vec<_>>()
         );
     }
     let mut fixup = Vec::new();
     if !ds_status.unsure.is_empty()
         && (display_states.modified || display_states.clean)
     {
         let p1 = repo.dirstate_parents()?.p1;
         let manifest = repo.manifest_for_node(p1).map_err(|e| {
             CommandError::from((e, &*format!("{:x}", p1.short())))
         })?;
         for to_check in ds_status.unsure {
             if unsure_is_modified(repo, &manifest, &to_check.path)? {
                 if display_states.modified {
                     ds_status.modified.push(to_check);
                 }
             } else {
                 if display_states.clean {
                     ds_status.clean.push(to_check.clone());
                 }
                 fixup.push(to_check.path.into_owned())
             }
         }
     }
     let relative_paths = (!ui.plain())
         && config
             .get_option(b"commands", b"status.relative")?
             .unwrap_or(config.get_bool(b"ui", b"relative-paths")?);
     let output = DisplayStatusPaths {
         ui,
         no_status,
         relativize: if relative_paths {
             Some(RelativizePaths::new(repo)?)
         } else {
             None
         },
     };
     if display_states.modified {
         output.display(b"M", ds_status.modified)?;
     }
     if display_states.added {
         output.display(b"A", ds_status.added)?;
     }
     if display_states.removed {
         output.display(b"R", ds_status.removed)?;
     }
     if display_states.deleted {
         output.display(b"!", ds_status.deleted)?;
     }
     if display_states.unknown {
         output.display(b"?", ds_status.unknown)?;
     }
     if display_states.ignored {
         output.display(b"I", ds_status.ignored)?;
     }
     if display_states.clean {
         output.display(b"C", ds_status.clean)?;
     }
 
     let mut dirstate_write_needed = ds_status.dirty;
     let filesystem_time_at_status_start = ds_status
         .filesystem_time_at_status_start
         .map(TruncatedTimestamp::from);
 
     if (fixup.is_empty() || filesystem_time_at_status_start.is_none())
         && !dirstate_write_needed
     {
         // Nothing to update
         return Ok(());
     }
 
     // Update the dirstate on disk if we can
     let with_lock_result =
         repo.try_with_wlock_no_wait(|| -> Result<(), CommandError> {
             if let Some(mtime_boundary) = filesystem_time_at_status_start {
                 for hg_path in fixup {
                     use std::os::unix::fs::MetadataExt;
                     let fs_path = hg_path_to_path_buf(&hg_path)
                         .expect("HgPath conversion");
                     // Specifically do not reuse `fs_metadata` from
                     // `unsure_is_clean` which was needed before reading
                     // contents. Here we access metadata again after reading
                     // content, in case it changed in the meantime.
                     let fs_metadata = repo
                         .working_directory_vfs()
                         .symlink_metadata(&fs_path)?;
                     if let Some(mtime) =
                         TruncatedTimestamp::for_reliable_mtime_of(
                             &fs_metadata,
                             &mtime_boundary,
                         )
                         .when_reading_file(&fs_path)?
                     {
                         let mode = fs_metadata.mode();
                         let size = fs_metadata.len() as u32 & RANGE_MASK_31BIT;
                         let mut entry = dmap
                             .get(&hg_path)?
                             .expect("ambiguous file not in dirstate");
                         entry.set_clean(mode, size, mtime);
                         dmap.add_file(&hg_path, entry)?;
                         dirstate_write_needed = true
                     }
                 }
             }
             drop(dmap); // Avoid "already mutably borrowed" RefCell panics
             if dirstate_write_needed {
                 repo.write_dirstate()?
             }
             Ok(())
         });
     match with_lock_result {
         Ok(closure_result) => closure_result?,
         Err(LockError::AlreadyHeld) => {
             // Not updating the dirstate is not ideal but not critical:
             // don’t keep our caller waiting until some other Mercurial
             // process releases the lock.
         }
         Err(LockError::Other(HgError::IoError { error, .. }))
             if error.kind() == io::ErrorKind::PermissionDenied =>
         {
             // `hg status` on a read-only repository is fine
         }
         Err(LockError::Other(error)) => {
             // Report other I/O errors
             Err(error)?
         }
     }
     Ok(())
 }
 
 fn ignore_files(repo: &Repo, config: &Config) -> Vec<PathBuf> {
     let mut ignore_files = Vec::new();
     let repo_ignore = repo.working_directory_vfs().join(".hgignore");
     if repo_ignore.exists() {
         ignore_files.push(repo_ignore)
     }
     for (key, value) in config.iter_section(b"ui") {
         if key == b"ignore" || key.starts_with(b"ignore.") {
             let path = get_path_from_bytes(value);
             // TODO: expand "~/" and environment variable here, like Python
             // does with `os.path.expanduser` and `os.path.expandvars`
 
             let joined = repo.working_directory_path().join(path);
             ignore_files.push(joined);
         }
     }
     ignore_files
 }
 
 struct DisplayStatusPaths<'a> {
     ui: &'a Ui,
     no_status: bool,
     relativize: Option<RelativizePaths>,
 }
 
 impl DisplayStatusPaths<'_> {
     // Probably more elegant to use a Deref or Borrow trait rather than
     // harcode HgPathBuf, but probably not really useful at this point
     fn display(
         &self,
         status_prefix: &[u8],
         mut paths: Vec<StatusPath<'_>>,
     ) -> Result<(), CommandError> {
         paths.sort_unstable();
         for StatusPath { path, copy_source } in paths {
             let relative;
             let path = if let Some(relativize) = &self.relativize {
                 relative = relativize.relativize(&path);
                 &*relative
             } else {
                 path.as_bytes()
             };
             // TODO optim, probably lots of unneeded copies here, especially
             // if out stream is buffered
             if self.no_status {
                 self.ui.write_stdout(&format_bytes!(b"{}\n", path))?
             } else {
                 self.ui.write_stdout(&format_bytes!(
                     b"{} {}\n",
                     status_prefix,
                     path
                 ))?
             }
             if let Some(source) = copy_source {
                 self.ui.write_stdout(&format_bytes!(
                     b"  {}\n",
                     source.as_bytes()
                 ))?
             }
         }
         Ok(())
     }
 }
 
 /// Check if a file is modified by comparing actual repo store and file system.
 ///
 /// This meant to be used for those that the dirstate cannot resolve, due
 /// to time resolution limits.
 fn unsure_is_modified(
     repo: &Repo,
     manifest: &Manifest,
     hg_path: &HgPath,
 ) -> Result<bool, HgError> {
     let vfs = repo.working_directory_vfs();
     let fs_path = hg_path_to_path_buf(hg_path).expect("HgPath conversion");
     let fs_metadata = vfs.symlink_metadata(&fs_path)?;
     let is_symlink = fs_metadata.file_type().is_symlink();
     // TODO: Also account for `FALLBACK_SYMLINK` and `FALLBACK_EXEC` from the
     // dirstate
     let fs_flags = if is_symlink {
         Some(b'l')
     } else if has_exec_bit(&fs_metadata) {
         Some(b'x')
     } else {
         None
     };
 
     let entry = manifest
         .find_file(hg_path)?
         .expect("ambgious file not in p1");
     if entry.flags != fs_flags {
         return Ok(true);
     }
     let filelog = repo.filelog(hg_path)?;
+    let fs_len = fs_metadata.len();
+    // TODO: check `fs_len` here like below, but based on
+    // `RevlogEntry::uncompressed_len` without decompressing the full filelog
+    // contents where possible. This is only valid if the revlog data does not
+    // contain metadata. See how Python’s `revlog.rawsize` calls
+    // `storageutil.filerevisioncopied`.
+    // (Maybe also check for content-modifying flags? See `revlog.size`.)
     let filelog_entry =
         filelog.data_for_node(entry.node_id()?).map_err(|_| {
             HgError::corrupted("filelog missing node from manifest")
         })?;
     let contents_in_p1 = filelog_entry.data()?;
+    if contents_in_p1.len() as u64 != fs_len {
+        // No need to read the file contents:
+        // it cannot be equal if it has a different length.
+        return Ok(true);
+    }
 
     let fs_contents = if is_symlink {
         get_bytes_from_os_string(vfs.read_link(fs_path)?.into_os_string())
     } else {
         vfs.read(fs_path)?
     };
     Ok(contents_in_p1 != &*fs_contents)
 }